Help Playing Music Through Car Stereo via USBSupport

I installed a JVC In Dash into my car today and it came with no aux. input, only usb. I was disappointed when I plugged my DHD into the usb and found I could not play my music. Is there a special trick to doing this? I didnt opt for the bluetooth module as I would rather not play my music via bluetooth due to the fact sound quality suffers.

sorry if this has already been covered, I found lots of topics but wasn't if it mattered on what device is being used.